Cracking blended heavy crudes



Oct. 26, 1943. R, M; |-||1 2,332,794

cRAcxING BLENDED HEAVY calms Filed Npv. 13, 1939 CONDE N SER Patented Oct. 26, 1943 CRACKING BLENDED HEAYY `CRIUDES Ralph M. Hill, Cranford, N. J., assignor to Standn ard Oil Development Company, a corporation of Delaware Application November 13, 1939, Serial No. 303,985

` V2 claims. (c1, 19e- 50) l i The present invention relates to improvements Vin the conversion of hydrocarbon oils, catalytically or thermally, to produce motor` fuels of "the gasoline type; and more particularly, this invention relates to improvements in which a gas oil, which normally is a high coke producing feed stock in the type of operation here in question, is blended with a `recycled oil, such as a virgin or cracked gas oil which has lower coke forming tendencies, and subjected to a cracking operation, whereupon a gasoline of high octane number is produced, as well as a fuel oil of good quality, the amount of coke formed during the conversion being relatively small.

One object of the present invention is to carry out a catalytic cracking operation under conditions such that a good yieldof gasoline is obhas lower coke forming tendencies than the viscosity-broken reduced crude, and then subject the mixture to a catalytic cracking operation.

Reference is had at this point to the accompanying drawing which shows diagrammatically,

in partial vertical section, apparatus means for carrying the present invention into effect.

In the drawing, a feed, such as a reduced crude, iscracked in viscosity breaker26 and is introduced into the cracking system from reservoir I through line 2 and atV the same time a gas oil, which may have been produced in a cracking opera-tion, may be discharged from reservoir 3 into line 4 and from there into mixing chamber 5, where it is admixed in suitable proportion with a viscosity-broken product from reservoir I.

It will be understood that, `as an obvious modification of the foregoing, the viscosityebreaking reactor 26 may be in direct communication with line 2 thus lay-passing reservoir l and the product may retain substantially all of the heat content it acquired from the viscosity-breaking process. Also the gas oil in reservoir 3 maybe a gas oil obtained by distillation from the original hydrocarbon feed stock. t

The blend of viscosity-broken hydrocarbon oil chamber shown is of the tray type.

and gas oil is discharged from vessel `5 into line 6 and thence into a secondary bubble tower I'I where hydrocarbons boiling Ywithin the gasoline range are Stripped from the said blend. The higher boiling hydrocarbons containing' the blend are withdrawn through line 1, and after that, pumped through line 'la into heating coil 8, Where it is vaporized. YThe vaporized material is discharged into line I0 and from there into the bottom of reaction chamber II. The reaction This type of reactor may be provided according to known methods, with intake and discharge manifolds externally disposed and in communication with the reactor, which manifolds permit parallel iiow of vapors through several beds of catalyst, i. e. the vapors may be permitted to flow into the reactor kthrough several branch pipes leading from a common manifold and then flow upwardly or downwardly through the bedsoi catalyst C, supported on perforated trays and then issue from the reactor through several branch pipes into a e common manifold pipe.`

This manifolding means is notshown .in the drawing. According to the drawing the vapors would flow serially through the several beds. Oi course, it would also be possible `to provide one continuous bed of catalyst in reactor Il.

From reactor I I, the vapors are discharged into line I2 and from there, into primary bubble tower I4. The bottoms from'this towerare withdrawn through line I5 and caused to flow into line 'la for recycling purposes, or if this fraction becomes too refractory for further cracking, it may be withdrawn from the system through line I5a for use as a fuel oil. The overhead product from bubble tower I4 is discharged through line IE `into the previously mentioned secondary bubble tower I1, the gasoline vapors from this tower issuing through line I8, then passing through condenser I9, thence passing into receiving drum 20, the fixed gas being withdrawn through line ZI and the gasoline recovered through line 22.

Periodically the vcatalyst-C in chamber II will requireregeneration and for that purpose, the valves in lines I0 and I2 are closed and a purging gas is forced into the reactor through line 2t and withdrawn through line 24. This purging gas may be steam, ue gas, nitrogen or the like.

After purging, a regeneration gas may be forced i The feedwas contacted with an eration gasmay be air diluted with flue gas, steam, N2 or the like, to the extentthat it contains about 1 to 10% free oxygen. If the catalyst is an acid treated clay, the temperature of the regeneration oxidation should not exceed about 1000 F. to 1100 F., but if a synthetic gel catalyst is employed, the regeneration may be carried out at a somewhat higher temperature, say' 1200D F. The details of regeneration of a catalyst of this type are well known to the art.

It may be saidVV that two reactors such as I l may be employed in- I the present process so that `while ,one vbody `ofvgju'.-

' at a 'temperature of 774`F.ata feed rate ofy 1.2

volumes of reduced crude jpervolume of catalyst per hour, the oil lbeing measured on- `a cold oil basis. f f

The foregoing process yieldedY the following: l Wet-gas weight per c'ent 1; Gasoline volume per cent f 4. Material with lowest boiling of'400 F `do 92.' Coke weight 'per cent 1.

Thematerial boiling at 400 E'. and above'liad an A.P. I. gravity of 17.4 and a Euro1 vviscosity at 122 F. oi 28.0. y i,

In order toshowthe advantage of employing the presentv process the followingv examples are given in the irst of which the material derived Y from the viscositv-breakingA operation boiling at and above 40.0 F. Was catalytically cracked and in the second, the same material 'was mixed with a. cracked gas oil oflow coke forming propensities and then cracked.

Example 1 In this example the oil boiling at 400 E. and

above was contacted with a bed of catalyst, the

feed: rate being 0.6 volumeof oil per volume of catalyst per hour on a cold oil basis. The-temperature in the reaction AZone was 850 'Ifhe 4catalyst employed was an acidtreated clay. The catalyst was maintained at a temperaturey of 850 F. `during the cracking operation. 'Iiheproc-` ess yielded:

Wet gas per cent by weight" 4.2

Gasoline percentb'y voluine r23.52'

Gas oil do 64.5

Coke l per cent by weight" 10.6

Example 2 In this experiment two parts 'oy volume' of; the ro'ateiialboiling at and above 400 F. in tl'i'e previous example was mixed with one 'part of a gasoil resulting from the catalytic cracking of an East Texas virgin gas oil in which the gas cil produced in the cracking process had low coke forming tendencies. The mixture lwas ysubjected to the following conditions:

was maintained at a temperature of 903 F. rihe process yielded the following:

Wet gas per cent by weight 6.1 Gasoline per cent by volurne 39.6 Gas oil do 50.5 Coke per cent; by weight 8.8

The gravity of gas oilwas 21.3 A. l?. I.

It will be noted from the foregoing examples that the straight gas oil when cracked according to the process of Example 1 gave a conversion `@23.2% of gasoline and 10.6% coke. When this gas oil was blended with the cracked gas o-il, the

conversion was 39.6% gasoline and 8.8% coke. It will thusbe seen that less coke was produced in the process oiTE'xample 2 than in the Example 1 process in spite of the fact that in Example 2 a acid treated clayv catalystat a ieed'rate of 1.2 volumes of'oil per volume of catalyst per hour. The catalyst much higher gasoline conversion was obtained thanin the run of Example 1. yThe temperature in the run of Example 2 was higher than the preceding run vbut this serves to emphasize more vclearly the value of the present invention since itis well known that when cracking in avgiven phase, vapor 0rliquid, higher temperatures or higher `gasoline conversions yield greater percentagesof coke. i

The precise details enumerated in the above examples obviously are notfixed-- and numerous modicationsfof the procedures of the examples maybe made by those skilled in this art without departing from the spirit of the invention. For

example, the ratio of gasoil or cycle oil that has 'a low coke forming tendency under cracking conditions to the gas oil having a relatively high coke forming tendencyniay vary from one half to four vor ive volumes ofthe former 'toene oi the latter,

withinconventional ranges. The octane number of the gasoline in aonce-through operation is rel atively high, say in the neighborhood of '75.` The present process is applicable to cracking gas oils, heavy naphthas and may be advantageously carried out inthe presence of hydrogen.`

I-Iaving described my invention, what I claim l. Ainethod of converting higher boiling hydrocarbons into lower boiling hydrocarbons suitable for motor fuel which comprises heating a heavy residual oil to reduce'its viscosity without extensive formation of motor fuel constituents, mixing the hot resulting viscosity-broken product with a cycle gas oil from a separate catalytic cracking process to supply` heat` thereto, fractionating the mixture to separate condensate oil higher boiling than about400 F. from lower boiling constituents, thecondensate oil containing constituents from theresidual. oil which-have a relatively high coke-forming tendency and constituentsfrom the cycle gas oil which have a relatively low coke-forming tendency, passing the condensate o il through a cracking zone maintained at 'activecracking temperature and containing ay cracking catalyst, `keeping the condensate oil withinsaid cracking zone for a time sufficient to form a substantial amount of lower boiling hydrocarbons and thereafter fractionating the crackedproducts to separate a motor fuel vfraction therefrom.

Z. A method of converting higher boiling hydrocarbons into lower boiling hydrocarbons suitable formotor fuel which comprises mixing a feed stock having a relatively high coke-forming tendency when cracked with an oil having a relatively low coke-forming tendency when cracked, fractionating the mixture in a rst fractionating zone in the presence of a light fraction produced in the process to separate a motor fuel fraction from higher boiling constituents, condensing the 10 motor fuel fraction, catalytically cracking the higher boiling constituents to form lower boiling hydrocarbons, fractionating the cracked products in a second fractionating zone to give a light fraction and a heavy fraction, recycling the heavy fraction to the catalytic cracking zone, and passing the light fraction to the said rst fractionating zone.

RALPH M. HILL. 

